1. Field of the Invention
The present invention relates to color conversion definition creating method and color conversion definition creating apparatus for creating a color conversion definition defining a relation of data conversion between RGB data representative of a combination of values of R (red), G (green) and B (blue) for a printer and CMYK data representative of a combination of values of C (cyan), M (magenta), Y (yellow) and K (black) for printing to perform printing in which a color of an image outputted by a printer receiving the RGB data and outputting the image is reproduced, and a color conversion definition creating program storage medium storing a color conversion definition creating program which causes a computer to operate as the color conversion definition creating apparatus when the color conversion definition creating program is incorporated into the computer.
2. Description of the Related Art
Hitherto, as an apparatus for applying a high quality of color processing for printing to image data representative of an image, there is known an apparatus (for example, Japanese Patent Application Gazette Hei.9-83824) in which upon receipt of CMY data representative of a combination of density values of C, M and Y, CMYK data representative of a combination of dot % of C, M, Y, and K is outputted.
This apparatus receives the CMY data and performs a color processing. Even recently, while there are proposed various improvements on such an apparatus, such an apparatus is concerned with a well-established technology in base, and there exist many skilled persons capable of operating such an apparatus to perform a high quality of color processing (this color processing is referred to “set up”).
Recently, as color management technologies have come into wide use, there is increased a necessity for obtaining a high quality of CMYK data for printing in accordance with color data other than the CMY data. As one of the examples, it may be required that upon receipt of RGB data representative of a combination of values of R, G, and B, an image, in which a color of a printed image obtained through an output of a printer based on the RGB data is faithfully reproduced, is printed.
In this case, it is considered that the RGB data is converted into the CMYK data using the apparatus proposed in the Japanese Patent Application Gazette Hei.9-83824 through conversion of the RGB data into the CMY data in accordance with any technique. As a technique of converting the RGB data into the CMY data, there is known a technique in which RGB is converted into a block CMY.
However, even if the RGB data is converted into the CMY data, and then converted into the CMYK data using the apparatus proposed in the above-mentioned Japanese Patent Publication Gazette, it is implied that the RGB data is converted into the CMYK data capable of obtaining a printed image which is reproduced into a color preferable for a skilled person by operation of the skilled person, and it involves “one's taste” for color. Thus, it is difficult to obtain the CMYK data capable of obtaining a printed image, in which a color of an image obtained through an output of a specified printer based on the RGB data is faithfully reproduced.
As another technique of converting the RGB data into the CMYK data, there is known a technique in which the RGB data is converted into calorimetric data such as L*a*b* data and XYZ data in accordance with a printer profile representative of color reproduction characteristics of the specified printer, while the CMYK data, which is associated with the same calorimetric data as that when the RGB data is converted into calorimetric data in accordance with the printer profile, is determined in accordance with a printing profile representative of color reproduction characteristics of a printing system with which a printed image intended to faithfully reproduce a color is obtained, so that the RGB data associated with the same calorimetric data is associated with the CMYK data. Thus, it is possible to convert the RGB data into the CMYK data representative of the same color on a calorimetric basis.
However, the RGB data consists of three variables of R, G and B, while the CMYK data consists of four variables of C, M, Y and K,. The CMYK data is concerned with the redundancy. And thus there exists a plurality of combinations of C, M, Y and K for one RGB data, which is same on a calorimetric basis. While the plurality of combinations corresponds to the same RGB data on a calorimetric basis, all the combinations have not a printing aptitude and combinations having the printing aptitude are restricted. A large factor as to whether there is the printing aptitude is a value of K. And in order to obtain the CMYK data capable of obtaining the same color on a calorimetric basis, there is a need to determine the value of K in accordance with a printing company, a printing machine and the like.
That is, the technology, in which the RGB data is converted into the CMY data, and then converted into the CMYK data using for example, the apparatus proposed in the above-mentioned Japanese Patent Publication Gazette, is no problem, since the value of K is adjusted by a skilled person to a value suitable for the printing company and the printing machine. However, it is difficult to faithfully reproduce a color of an image outputted by a specified printer in accordance with the RGB. On the other hand, in case of a technology of matching the calorimetric values, it involves a problem that it is difficult to obtain CMYK data having the printing aptitude.